The present invention is directed to a method for the true alignment of two fiber ends, wherein the fiber ends are illuminated to create a picture of the fiber ends, which picture is scanned with a picture-video sensor of a video camera.
U.S. Pat. No. 4,506,947, whose disclosure is incorporated herein by reference thereto, discloses a method for alignment of cores of optical fibers, wherein ultraviolet light is guided onto the two fiber ends of the light waveguides. The area of irregularity is contemplated via the optical lenses in two directions proceeding perpendicular relative to one another by means of a video camera and, thus, the obtained picture of the position of the fiber ends is displayed on a video screen. The operator can perform a true alignment by actuating the corresponding manipulators. The fiber core, which, due to the fluorescing light, pictures itself on the video screen differently from the fiber cover or cladding, serves as a basis for determining the position. A disadvantage of this method is that the contrast of the fiber core compared to the fiber cover is very low and can only be improved by an unproportionally greater effort regarding the imaging device. Such devices are applicable during manufacturing. However, because a device used in the field must have a small size, must be light-weight and must have a cost-saving design, this method and device is not presently usable out in the field. The very expensive imaging systems and the high resolution camera systems of this system cannot be justified in this context.
U.S. Pat. No. 4,452,506, whose disclosure is incorporated herein by reference thereto and which claims priority from the same British Patent Application as European Patent Specification B1 00 30 108, discloses alignment equipment for positioning two light waveguide ends wherein a test light is guided into one of the light waveguide ends on which not all is guided further in the core, given a complete, exact alignment of the two light waveguide ends. A portion of the light, then, will proceed outside in a parallel fashion to the longitudinal axis along the second light waveguide. For the detection of this portion of the outside proceeding light that is proportional to the misalignment between the waveguides, an arrangement of four sector-shaped photosensitive elements are provided in a plane extending transverse relative to the longitudinal axis of the light waveguide. These light-sensitive elements are allocated to corresponding evaluation circuits. Based on the measuring signals originating from the individual sectors, the size and the direction of the misalignment is determined and a post adjustment by means of corresponding adjustment elements is enabled. The disadvantage of such an arrangement is, above all, that the light-sensitive, sector-shaped elements must first be mounted or plugged onto the beam waveguide. For an optimally accurate measurement, however, a sliding position of the light-sensitive elements would actually be necessary, since every lateral play of these elements expresses itself in a measuring error. Furthermore, another disadvantage is that only the tips of the sectors lie in the area of the cover of the beam waveguides and the least amount of light is accepted there. This means that the sensitivity of the arrangement increasingly decreases with a decreasing misalignment so that a fine alignment of the ends can only be performed in relatively inaccurate fashions.
In a copending U.S. patent application, Ser. No. 755,276, which was filed on July 15, 1985 and claims priority from German Application No. 34 29 947, a measuring arrangement is disclosed. It is a prerequisite in this measuring method that light from the measuring emitter/waveform generator is coupled into a core of a light waveguide directly before the splicing location. Normally, this is achieved in that this beam waveguide is given a definite curvature, whereby behind the splicing location, likewise taking advantage of this bending method, the outcoupling of a portion of the light signal guided via the irregular location of the light of the fiber occurs. The application of such a coupling method in the form of bent waveguides is limited, but not possible, for example in the case of fibers that are barely sensitive to bending and curving, in which case the fiber with a special primary coating, for example a hermetically coated fiber, and always, then, when the fiber is not freely accessible, for example in the case of preconnected cables, so-called pigtails and in the case of particularly small projection lengths.